To some it’s music. To others it’s a racket. But Michael Ellis says those nocturnal crickets have a useful feature you might not expect.
I bet that the most of you, like me, have noticed that beginning in late August crickets begin chirping at night. And this pleasant chorus lasts all the way through the fall until the first big frost. These are male snowy tree crickets trying to attract a mate. They are very common and widespread. While they are mostly herbivorous they also eat aphids - a gardener’s friend. Assuming success for the crooning Casanovas, the females – which are very difficult to tell from the males – lay eggs in the bark of trees. Those eggs hatch the following spring and very slowly mature into adult tree crickets and by late summer they are ready to mate.
They are also known as the thermometer cricket. Way back in 1897 a professor at Tufts University figured out a formula to determine the ambient air temperature based on the number of chirps this cricket makes per minute. It's pretty darn accurate. You count the number of chirps in 13 seconds and then add the number 40 to get the temperature in Fahrenheit.
A little physiology. All animals except for birds and mammals have body temperatures that are governed by their surrounding environment.; that is, they are poikilotherms (Greek for “varying temperature.”) So as the world heats up the cricket’s own metabolic processes increase. When it gets warm enough, the males are able to start singing. They raise their wings to a 45-degree angle and draw the scraper of one wing across the furrows on the underside of the other wing. It is like running your finger along the teeth of a comb and presto - a loud sound from a small insect. This activity increases in direct proportion to the temperature.
There are other crickets, like the field cricket, who’s chirping can also be used but the snowy tree cricket is much more precise. Of course, these insects can only sing between 55 and 100°. So outside of that range, you'll have to rely on a thermometer.